Your IT department can watch your network pretty closely by using a variety of WHOIS lookup tools. You can identify hackers and spammers and report them to the proper authorities when there's a breach. You can also find out information about your site's visitors and competitors by using the WHOIS database.

There are a few basic searches you can do. Each one can help you find out different things, no matter how much or how little information you have to work with. Consider the following:

1. Perform a domain name WHOIS search. This is the most basic type of search but it's useful if all you have is a URL to work with.

2. Use WHOIS lookups to find the WHOIS registry information of a company. You can also find the location of servers and networks using an IP locator.

3. Do a reverse IP DNS lookup. This is a great tool if all you have is an IP address.

Action Steps
The best contacts and resources to help you get it done

Find the owner of a website using a WHOIS domain search

When a person or company buys a domain name, they are required to register their contact information with WHOIS. This information is kept in a public database and anyone can run a search to find the registration information associated with almost any domain name. All you need to perform this search is a domain name.

I recommend: Search the WHOIS database using GoDaddy.com. You can also use the search function at Whois.Net.

Try out an IP WHOIS lookup

An IP address is essentially the virtual address at which a network is located. It is expressed using four different numbers, separated by dots, ranging from zero to 255 (i.e. 143.78.39.10). These numbers actually represent binary numbers, but laypeople don't know how to read binary code so it's easier to express an IP address using regular digits. Note that IP addresses don't necessarily correspond with the physical address of a computer, but the server the computer is connected to (possibly that of the Internet Service Provider).

I recommend: Check out the IP lookup at GeekTools, which gives you all the WHOIS information associated with a given IP address. Search the entire WHOIS database at Network Solutions. Pinpoint the locations of people who visit your site using the lookup at IP2Location.com.

Run a reverse DNS search

'DNS' is an acronym for 'domain name server.' If all you have to track a hacker is an IP address, you can run it through a reverse DNS lookup to find out what host server his computer is connected to. Try running your own IP address through the lookup to see what results come up. This will give you some insight as to what information you can expect to receive when trying to find out about malicious emails or breaches in your network. Be aware that it is possible to hide an IP address, and in many cases, hackers cover their tracks well.

I recommend: Use the simple search feature at 12dt.com. You can also use the lookup at Search Engine Optimising.

Tips & Tactics

Helpful advice for making the most of this Guide

• •  You can hide your own IP address if necessary. If you need to remain anonymous for some reason, you can block your IP address so your server's information is not accessible when someone performs a reverse DNS search. This is the Internet equivalent of having an unlisted phone number.

Whois lookups provide a means of finding specific information for any website on the Internet. Each legitimate site and email carries identifiable numbers and names. Of course, a site engaged in illegal activity masks the whereabouts of its perpetrators. Nevertheless, whois lookup tools provide a necessary and free service for your business.

When someone registers a website or obtains an email address, two identifiable markers result. DNS (Domain Name Service) represents the hostname or website. Each website carries an identifiable numbered IP address (Internet Protocol). This number allows internet routers to move all Internet traffic around the world. A domain, DNS and whois IP lookup quickly retrieves information about ownership, servers and location—some engines provide more information. Use whois lookup searches to find the following:

1. Quickly find information on competitors' websites with a whois domain search.

2. Use reverse whois IP address lookup to get information on spammers and your website visitors.

3. Find whois websites that offer multiple tools and search engines for one-stop searches.

4. Locate specialized niche search engines.

Action Steps
The best contacts and resources to help you get it done

Get whois domain lookup for competitor websites

Find who owns any website with contact information, servers and pertinent historical dates.

I recommend: Go to InterNIC for domain names from .aero to .travel and search by Domain, Registrar or Nameserver. Enter a domain name at Name Intelligence, Inc., for free extended information that includes the website’s front page, indexed data, registry data, server data and whois record. Go to Whois.net and enter a website name, then obtain a SiteTiki.com article pertaining to the domain with interesting facts including front-page and Meta tags.

Search out a reverse IP DNS lookup for spammers and your website's visitors

A reverse DNS search translates a websites IP address to a hostname. Search email IP addresses to find legitimate senders and, if your web provider offers tools that lists your site's stats, decipher the IP addresses for visitors viewing your website.

I recommend: Go to iWEBTOOL and find other websites hosted on your IP address by entering a domain or IP address or see if any other website shares the same IP address. Visit ReverseIPLookup.net and enter any domain name to find shared addresses. Go to Expect IT, Ltd and enter either the host or IP address.

Locate whois lookup sites featuring multiple tools

These sites do more than locate the registry information of a domain name. Find several additional tools, such as whois IP lookup, DNS information and tracing.

I recommend: Go to Network Solutions for a domain name, NIC handle or whois IP lookup. Use lookup, trace, conversions or ping a domain name by selecting “Ping,” then typing the domain or IP address in the box at Network-Tools.com.

Do a specialized whois search with these tools

These websites provide tools typically unavailable on other search engines.

I recommend: To lookup educational domains ending in .edu, enter either name, nameserver or IP address at EDUCAUSE. See Tucows Inc. for an online input IDN Conversion Tool that converts international domain names or nameserver to Punycode. Search American Registry for Internet Numbers, ARIN WHOIS, that allows you to limit your search by attaching flags that includes query by record type, query by attribute, modify results with flags, record hierarchy and wildcard queries.

Tips & Tactics

Helpful advice for making the most of this Guide

• •  In the US, the non-profit corporation ICANN (Internet Corporation for Assigned Names and Numbers) maintains all responsibilities for coordinating the entire domain name system. The organization works with other global bodies in keeping uniformity with the DNS and IP system.